Direct Answer
Most structural steel shop drawings specify SSPC surface preparation (typically SP 6 Commercial Blast or SP 10 Near-White Blast) followed by a shop primer (commonly red oxide or zinc-rich primer to 2–3 mils DFT). The general notes sheet defines the specification; individual members with special coating requirements (galvanized, stainless, weathering steel) are flagged on their piece mark drawings.
Full Explanation
The Steel Structures Painting Council (SSPC, now AMPP) surface preparation standards define how clean the steel surface must be before paint. SP 6 Commercial Blast is standard for interior structural steel. SP 10 Near-White Blast is specified for aggressive environments or high-performance coatings. Primer DFT (Dry Film Thickness) is typically verified with a wet film gauge or DFT meter. Members that will be fireproofed in the field are sometimes left unprimed (bare metal) because primer can reduce fireproofing adhesion.
What This Means for Your Shop
Primer selection affects erection. Slip-critical connections require uncoated or specifically coated faying surfaces (Class A or B friction surfaces). Primed faying surfaces in a slip-critical connection are a code violation.
Common Mistakes
Priming the faying surfaces of a slip-critical connection with standard red oxide primer, which creates a Class C or D surface that doesn't meet the AISC slip coefficient requirement.
Recommended Process
Before blasting and priming, review the connection schedule for any slip-critical conditions. Mask or leave unprimed all slip-critical faying surfaces. Document the masking process and confirm at final inspection before shipping.